Feat: Add insert variable icon in the header of prompt editor. #4764 (#5142)

### What problem does this PR solve?

Feat: Add insert variable icon in the header of prompt editor. #4764

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/locales/en.ts

@@ -1179,6 +1179,7 @@ This delimiter is used to split the input text into several text pieces echo of
       addCategory: 'Add category',
       categoryName: 'Category name',
       nextStep: 'Next step',
+      insertVariableTip: `Enter / Insert variables`,
     },
     footer: {
       profile: 'All rights reserved @ React',

web/src/locales/zh-traditional.ts

@@ -1111,6 +1111,7 @@ export default {
       addCategory: '新增分類',
       categoryName: '分類名稱',
       nextStep: '下一步',
+      insertVariableTip: `輸入 / 插入變數`,
     },
     footer: {
       profile: '“保留所有權利 @ react”',

web/src/locales/zh.ts

@@ -1152,6 +1152,7 @@ General：实体和关系提取提示来自 GitHub - microsoft/graphrag：基于
       addCategory: '新增分类',
       categoryName: '分类名称',
       nextStep: '下一步',
+      insertVariableTip: `输入 / 插入变量`,
     },
     footer: {
       profile: 'All rights reserved @ React',